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Kernel/SysFS: Add Symbolic link functionality to the filesystem

This will be used later on to help connecting a node at /sys/dev/block/
that represents a Storage device to a directory in /sys/devices/storage/
with details on that device in that directory.
This commit is contained in:
Liav A 2022-04-22 20:35:15 +03:00 committed by Andreas Kling
parent 7e88bbe550
commit ecc29bb52e
4 changed files with 104 additions and 0 deletions

View file

@ -131,6 +131,31 @@ ErrorOr<void> SysFSInode::truncate(u64 size)
return m_associated_component->truncate(size); return m_associated_component->truncate(size);
} }
ErrorOr<NonnullRefPtr<SysFSLinkInode>> SysFSLinkInode::try_create(SysFS const& sysfs, SysFSComponent const& component)
{
return adopt_nonnull_ref_or_enomem(new (nothrow) SysFSLinkInode(sysfs, component));
}
SysFSLinkInode::SysFSLinkInode(SysFS const& fs, SysFSComponent const& component)
: SysFSInode(fs, component)
{
}
SysFSLinkInode::~SysFSLinkInode() = default;
InodeMetadata SysFSLinkInode::metadata() const
{
// NOTE: No locking required as m_associated_component or its component index will never change during our lifetime.
InodeMetadata metadata;
metadata.inode = { fsid(), m_associated_component->component_index() };
metadata.mode = S_IFLNK | S_IRUSR | S_IRGRP | S_IROTH | S_IXOTH;
metadata.uid = 0;
metadata.gid = 0;
metadata.size = 0;
metadata.mtime = TimeManagement::boot_time();
return metadata;
}
ErrorOr<NonnullRefPtr<SysFSDirectoryInode>> SysFSDirectoryInode::try_create(SysFS const& sysfs, SysFSComponent const& component) ErrorOr<NonnullRefPtr<SysFSDirectoryInode>> SysFSDirectoryInode::try_create(SysFS const& sysfs, SysFSComponent const& component)
{ {
return adopt_nonnull_ref_or_enomem(new (nothrow) SysFSDirectoryInode(sysfs, component)); return adopt_nonnull_ref_or_enomem(new (nothrow) SysFSDirectoryInode(sysfs, component));

View file

@ -62,6 +62,19 @@ protected:
NonnullRefPtr<SysFSComponent> m_associated_component; NonnullRefPtr<SysFSComponent> m_associated_component;
}; };
class SysFSLinkInode : public SysFSInode {
friend class SysFS;
public:
static ErrorOr<NonnullRefPtr<SysFSLinkInode>> try_create(SysFS const&, SysFSComponent const&);
virtual ~SysFSLinkInode() override;
protected:
SysFSLinkInode(SysFS const&, SysFSComponent const&);
// ^Inode
virtual InodeMetadata metadata() const override;
};
class SysFSDirectoryInode : public SysFSInode { class SysFSDirectoryInode : public SysFSInode {
friend class SysFS; friend class SysFS;

View file

@ -57,6 +57,53 @@ mode_t SysFSComponent::permissions() const
return S_IRUSR | S_IRGRP | S_IROTH; return S_IRUSR | S_IRGRP | S_IROTH;
} }
ErrorOr<size_t> SysFSSymbolicLink::read_bytes(off_t offset, size_t count, UserOrKernelBuffer& buffer, OpenFileDescription*) const
{
auto blob = TRY(try_to_generate_buffer());
if ((size_t)offset >= blob->size())
return 0;
ssize_t nread = min(static_cast<off_t>(blob->size() - offset), static_cast<off_t>(count));
TRY(buffer.write(blob->data() + offset, nread));
return nread;
}
ErrorOr<NonnullOwnPtr<KBuffer>> SysFSSymbolicLink::try_to_generate_buffer() const
{
auto return_path_to_mount_point = TRY(try_generate_return_path_to_mount_point());
if (!m_pointed_component)
return Error::from_errno(EIO);
auto pointed_component_base_name = MUST(KString::try_create(m_pointed_component->name()));
auto pointed_component_relative_path = MUST(m_pointed_component->relative_path(move(pointed_component_base_name), 0));
auto full_return_and_target_path = TRY(KString::formatted("{}{}", return_path_to_mount_point->view(), pointed_component_relative_path->view()));
return KBuffer::try_create_with_bytes("SysFSSymbolicLink"sv, full_return_and_target_path->view().bytes());
}
static ErrorOr<NonnullOwnPtr<KString>> generate_return_path_to_mount_point(NonnullOwnPtr<KString> current_path, size_t remaining_hop)
{
if (remaining_hop == 0)
return current_path;
auto new_path = TRY(KString::formatted("../{}"sv, current_path->view()));
remaining_hop--;
return generate_return_path_to_mount_point(move(new_path), remaining_hop);
}
ErrorOr<NonnullOwnPtr<KString>> SysFSSymbolicLink::try_generate_return_path_to_mount_point() const
{
auto hops_from_mountpoint = TRY(relative_path_hops_count_from_mountpoint());
if (hops_from_mountpoint == 0)
return KString::try_create("./"sv);
auto start_return_path = TRY(KString::try_create("./"sv));
return generate_return_path_to_mount_point(move(start_return_path), hops_from_mountpoint);
}
SysFSSymbolicLink::SysFSSymbolicLink(SysFSDirectory const& parent_directory, SysFSComponent const& pointed_component)
: SysFSComponent(parent_directory)
, m_pointed_component(pointed_component)
{
}
ErrorOr<void> SysFSDirectory::traverse_as_directory(FileSystemID fsid, Function<ErrorOr<void>(FileSystem::DirectoryEntryView const&)> callback) const ErrorOr<void> SysFSDirectory::traverse_as_directory(FileSystemID fsid, Function<ErrorOr<void>(FileSystem::DirectoryEntryView const&)> callback) const
{ {
MutexLocker locker(SysFSComponentRegistry::the().get_lock()); MutexLocker locker(SysFSComponentRegistry::the().get_lock());
@ -91,6 +138,11 @@ ErrorOr<NonnullRefPtr<SysFSInode>> SysFSDirectory::to_inode(SysFS const& sysfs_i
return TRY(SysFSDirectoryInode::try_create(sysfs_instance, *this)); return TRY(SysFSDirectoryInode::try_create(sysfs_instance, *this));
} }
ErrorOr<NonnullRefPtr<SysFSInode>> SysFSSymbolicLink::to_inode(SysFS const& sysfs_instance) const
{
return TRY(SysFSLinkInode::try_create(sysfs_instance, *this));
}
ErrorOr<NonnullRefPtr<SysFSInode>> SysFSComponent::to_inode(SysFS const& sysfs_instance) const ErrorOr<NonnullRefPtr<SysFSInode>> SysFSComponent::to_inode(SysFS const& sysfs_instance) const
{ {
return SysFSInode::try_create(sysfs_instance, *this); return SysFSInode::try_create(sysfs_instance, *this);

View file

@ -56,6 +56,20 @@ private:
InodeIndex m_component_index {}; InodeIndex m_component_index {};
}; };
class SysFSSymbolicLink : public SysFSComponent {
public:
virtual ErrorOr<size_t> read_bytes(off_t, size_t, UserOrKernelBuffer&, OpenFileDescription*) const override final;
virtual ErrorOr<NonnullRefPtr<SysFSInode>> to_inode(SysFS const& sysfs_instance) const override final;
protected:
ErrorOr<NonnullOwnPtr<KString>> try_generate_return_path_to_mount_point() const;
ErrorOr<NonnullOwnPtr<KBuffer>> try_to_generate_buffer() const;
explicit SysFSSymbolicLink(SysFSDirectory const& parent_directory, SysFSComponent const& pointed_component);
RefPtr<SysFSComponent> m_pointed_component;
};
class SysFSDirectory : public SysFSComponent { class SysFSDirectory : public SysFSComponent {
public: public:
virtual ErrorOr<void> traverse_as_directory(FileSystemID, Function<ErrorOr<void>(FileSystem::DirectoryEntryView const&)>) const override; virtual ErrorOr<void> traverse_as_directory(FileSystemID, Function<ErrorOr<void>(FileSystem::DirectoryEntryView const&)>) const override;